Rotor for rotating-wing aircraft



Oct. 8, 1940. H, FgCKE 2,217,106

ROTOR FOR RTATING-WING AIRCRAFT Filed Feb 18, 1938.

Patented Oct. 8, 1940 UNITED -sTATl-:s- PATENT ol-FlcaA Henrich Focke, Bremen, Germany ApplicationFebruary 18, 1938, Serial No. 191,327

I In Germany August 16, 1937 6 Claims.

'I'his invention concerns rotor devices for rotating-wing aircraft, of the kind comprising a plurality of blades jointed to the hub.

An important object of the invention is to provide interconnections adapted for inuencing the rotor blades in such manner that the latter will constantly tend to maintainprecise angular intervals between themselves.

The blades of air-screws have 4been braced tof- 10 gether in order to maintain their angular positions. For example, a. bracing of this kind was provided by Oehmichen (France) in his helicopter No. 3 of the year 1928.

Furthermore, it is known to provide ties for vl5 interconnecting the blades of a lifting screw, the eiect of these ties being to maintain the angle of incidence of the blades as well as the angular intervals between them. In this arrangement, fittings for the attachment of -ties extending forwardly from the blades, were of a height different from that of ttings for the at tachment of ties extending rearwardly from the blades.

In order to ensure balanced running of the rotor it is essential constantly to ensure the precision of the angularsetting o! the blades between themselves, and no solution ofthe problem involved is to be found in the arrangements previously proposed. The problem, however, is solved lby the presen invention which utilizes varyingtension in the blade interconnections for influencing the angles` of incidence of the several blades so that the latter have the above-stated tendency, namely, constantly to maintain precise angular intervals vbetween themselves. Thus, for example, if a blade lags in the direction of rotation, its angle of incidence is reduced by the pull of an interconnection, thereby reducing the airresistance on this blade and enabling it to overtake. If a blade overruns, the converse takes place with the result that the blade in question has a degree of lag.

VFurther features `of the invention will appear from the following description having reference to the annexed drawing wherein, Figure lillu'strates one constructional example in perspective and more or less diagrammatically and Figure 2 discloses a further embodiment thereof. In the drawing', blades a of a rotor -are shown partly broken away for sake of clearness. Each blade a which may be built up on a main tubular spar and ribs, has a column or arm b, preferably of stream-lined shape, mounted upon it, Y

5 5 the said column or arm inthe examples illustrated being extended from the main spar. The tips of the consecutive columns or `arms b are connected by tension' members c one carried forward to each preceding blade in the direction of rotation indicated by the arrow A and 5 one carried rearwardly to each following bladeA and connected in a similar manner thereto. The blade a which is jointed to the hub by the universal joint e, ispas shown in Figure 2, also mounted in a bearing sleeve f so as to be rotat- 1. able about the axis of its spar. Thus, in the revolutions of the rotor around the vertical or lifting axis g, each blade is capable of making an overtaking or a lagging movement or a. apping movement due to the provision of the uni 15 versal jointe, or a rotational movement abr-.it the axis of the spar due to its mounting in the sleeve f. The rotational movement, however, is

limited by the springs ii which are suitably anchored at their lower ends and connected at 20 their upperA ends with the extremities of a twoarmed vlever h. Thus, the blade always tends to assume a certain angle of incidence which is determined by the tensioning of the springs i i.

In operation, if the blade a lags relatively to 25 its preceding blade in the direction of revolution A, then the tension of the member c is increased, either immediately, or after the execution of a small lagging movement if the member c was not previously tensioned. Under the pull of the 30 member d becomes tensioned to cause a reverse tilting of the column b and a consequent increase 40 in the angle of incidence of the blade. The resultant increase in air resistance on the blade then causes the latter to lag, so 'that again the required condition is restored.

Instead of rotatably mounting the blade by 46 means of the bearing sleeve f and employing springs i i for adjusting the bladerotatively as in Figure 2, in some cases the natural torsional elasticity of the blade and its spar may sumce for obtaining a similar eifect. Such construction 50 is illustrated in Figure 1.

1. A rotor for helicopter type aircraft comprising in combination, a huba plurality oi blades radiating from said hub, said blades being constructed for adjustment of incidence angle, a drag joint betweeneach blade and the hub whereby blade spacing' may be varied by unequal lagging or leading oi' the blades, a blade tilting arm on each blade and means connecting each arm to the arms of the preceding and succeeding blades whereby the angle of incidence of a misplaced blade is changed until it regains its proper spacing. l

2. A rotor for helicopter type vaircraft comprising in combination, a hub, a plurality of blades radiating from said hub, said blades being constructed for adjustment of incidence angle, a drag joint between each blade and the hub whereby blade spacing may be varied by unequal lagging or leading of the blades, means associating each blade with the contiguous blades, said means being constructed to change the angle of incidence of any blade upon a change of its spacing with respect to said contiguous blades.

3. A rotor for helicopter type aircraft comprising in combination, a hub, a plurality of blades, means joining each blade to the hub for rotation thereof to change the angle of incidence, a dra'g joint between each blade and the hub permitting unequal blade spacing, an arm on each blade outwardly of all joints and extending upward from the plane of rotation thereof, and a tension member connecting the end of each arm to the end of the arm on the preceding blade whereby any change of blade spacing produces va change of the angle of incidence of the affected blade. y

4. In an aircraft rotor comprising blades each built up on a main longitudinal spar, a rotor hub,

blade mountings on the rotor hub so adapted that the incidence of the blades can be adjusted by natural torsional ilexibility thereof, drag joints between the blades and hub, a crank arm rigidly mounted on each spar beyond the drag joint, and upstanding from'the blade, and tensional interconnections between adjacent arms.

5. A rotor for helicopter type aircraft comprising in combination, a hub, a plurality of blades, means pivoting each blade to said hub for ro'tation to adjust the angle of incidence thereof, spring means connecting each blade and hub and tending constantly to preserve a predetermined angle of incidence, a drag joint for each .blade outwardly of said pivoting means, an arm extending upwardly from each blade, and a tension member connecting the upper end of each arm tothe upper end of the arm of the preceding blade. i

6. A rotor for helicopter type"`aircraft comprising in combination, a hub, a plur'ablity of blades, means pivoting each blade to said hub for rotation to adjust the angle of incidence thereof,

spring means connecting each blade and hub and tending constantly to preserve a predetermined angle of incidence, a drag joint for each blade outwardly of said pivoting means, an arm extending upwardly from each blade, a tension member connecting the upper end of each arm to the upper end of the arm of the preceding blade, and means to simultaneously adjust the lsaid predetermined angle of incidence of al1 blades.

HENRICH FOCKE. 

